dublin institute of technology msc in chemical and pharmaceutical process technology 30-apr-09...

Dublin Institute of TechnologyMSc in Chemical and Pharmaceutical Process Technology

30-Apr-09

Preparation of Ultra Pure Water

A focus on Membrane Separations

by Pat Reynolds 30-Apr-09

Semiconductor

Power

Pharma

30-Apr-09 Dublin Institute of TechnologyMSc in Chemical and Pharmaceutical Process Technology2

Today’s Presentation

90%

• Introduction to pure water applications

• Pure water quality requirements– Semiconductor, Power, Pharmaceutical

• Water Contaminants

• Membrane Processes– MF, UF, RO

• Ion Exchange– EDI

• Semiconductor Industry Water– Water use Process Flow– UPW Process Flow

• High Efficiency RO (HERO)

• Q & A’s


Introduction – Pure Water

• Semiconductor Industry– Ultra Pure Water (UPW) is used as an aggressive solvent to

wash a wafer many times during its fabrication.– Trace amounts of impurities in UPW can result in increased

defects and reduce yield

• Power Industry– Boiler feed water

• Pharmaceutical Industry– Purified Water – Wafer for Injection– GMP standards for production and quality

• A continuous supply of consistently pure water is critical to the profitability of a company.


Semiconductor UPW quality requirements

• Table values ("targets") generally are typical levels, not best available technology

• Tables should be used as guidelines only, not as specifications. Every parameter for each application should be reviewed and justified.

International Technology Roadmap for Semiconductors (ITRS) 2006 www.public.itrs.net


Reference only – refer to USP and Eur. Ph. For up-to-date figures


Boiler Feed Water• Water contaminants must be limited to prevent scaling,

corrosion and foaming.– pH, Hardness, Oxygen, Carbon dioxide, Silicates, Dissolved

solids, Suspended solids, Organics

• Control limits– Conductivity is used as an indicator of total ion contaminants

with an upper limit of 1 mOhm-cm but plants usually operate at 5 to 10 mOhm-cm and 10 to 20 ppb silica.

– Other ionic contaminants listed above are usually < 2ppb

• Water Treatment includes– Reverse Osmosis– Ion Exchange– EDI


Water Contaminants (1)-> S.E.M. -> OPTICAL MICROSCOPE -> VISIBLE TO NAKED EYE

MICRON

ANGSTROM

MOLECULARWEIGHT

->CLARIFIERS, MEDIA FILTERS

<---ULTRA---><---NANO---><---HYPER---> <---MICRO---> <------------------------------PARTICLE------------------------------>

-> RO'S

-> 0.1 PORES

-> 0.01 PORES -> BAG FILTERS, CARTRIDGE

<-POLLENS-><-BEACH SAND->

EXAMPLES

<-HUMAN HAIR->

->ENDOTOXIN, PYROGEN<-'

<-COAL DUST->

<-METAL IONS->

<-BACTERIA->

-> LOW PRESSFILTRATION

TECHNOLOGY

<-AQUEOUS SALTS-><-COLLOIDS-><-VIRUSES->

200 20,000 200,000 2,000,000

10,000 100,000 1,000,000 10,000,0001 10 100 1,000

1 10 100 10000.0001 0.001 0.01 0.1

SUSPENDEDDISSOLVED


Water Contaminants (2)

Dissolved Suspended

Charged Uncharged

Ions

Organics Organics Organics

Silica Silica Silica

Gases

Living particles (Bacteria, Fungi, algae etc.)

Non living particles (Sand, silt, precipitates)



Natural Organic Matter (NOM)

Humic Acids

Fulvic Acids

Colloidal Organic Carbon

Dissolved Organic Carbon (DOC)

Total Organic Carbon (TOC)Total Organic Carbon (TOC)

Polysaccharides



• Gases– Dissolved Oxygen – contributes to unwanted native oxide growth on silicon

wafers and must be minimized in UPW.– Carbon Dioxide (Alkalinity)

• Acts as a contaminant • Changes with pH


Membrane Processes

Used across industry in

water purification


Microfiltration/Ultrafiltration

Water Quality Multimedia MF UF

Turbidity (NTU)

0.5 < 0.1 < 0.1

SDI15 3 - 5 < 3 < 2

Filtrate Water Quality of membrane versus conventional pre-treatment

• Membrane Material– polysulfones, polypropylene, and polyvinylidene fluoride (PVDF).

• Physical configurations – hollow fiber, spiral wound, cartridge, and tubular.

• Particle removal capability– MF down to 0.1- 0.2 microns.– UF down to 0.005-0.01 microns.

• Driving force– Pressure or vacuum.

Microfiltration Modules

Tubular


Ultrafiltration modules


Osmosis

• The tendency of water to pass through a semi-permeable membrane, into a solution of higher concentration.

Strong salt solution

Pure WaterWater

Semipermeable membrane

Time = 0 Time = Equilibrium


What is Reverse Osmosis? • Reverse osmosis is the reversal of the standard flow of materials

in osmosis

• Pressure is applied to over come osmotic pressure, reversing osmosis

• Flow from higher salt concentration to lower salt concentration side.

Apply Pressure

Semi permeable

• Flow rate of water through the membrane is pressure dependent reducing the cconcentration of salts in the pure water side of the membrane will be lower

• RO membranes are effectively non-porous. The transport of a molecule across the membrane is diffusion controlled as described the solution-diffusion transport equation

• Salt passage through the membrane is not a function of pressure, is only a function of salt concentration


FORCES ACTING ON THE MEMBRANE

• Osmotic Pressure: The pressure differential across a semi permeable membrane, due to the salt concentration gradient.

• Applied pressure: e.g. head pressure

1000mg/l salt solution

300mg/l salt soln

Water

10psi

3psi

7psi

100mg/l TDS = 1psi

Water

4.6ft

2.3ft

2.3 ft water column = 1psi

1psi

2psi

1psi


Applying pressure to reverse the natural process osmosis

1000mg/l salt solution

300mg/l salt soln

10psi

3psi

Water

1psi

91psi

83psi

2.3ft

90psi Time = 0 Time = Equilibrium

Osmotic pressure

Applied pressure

Net driving pressure


Exercise

3000 mg/l 20 mg/l

200 psi

Osmotic PressureApplied Pressure

50 psi

NDP

a) Osmosis

b) Reverse Osmosis

??

?

?

?

?


RO transport Equations 1a

• RO membranes are effectively non-porous. The transport of a molecule across the membrane is diffusion controlled as described the solution-diffusion transport equation

)( pLN Aw

• where NAw is the water flux through the membrane, Δp is the trans membrane pressure difference, Δπ is the difference in osmotic pressure between the feed and the permeate, and L is a constant describing the physical characteristics of the membrane itself

• Flow rate of water through the membrane is pressure dependent • Concentration of salts in the pure water side of the membrane will be lower


RO transport Equations 1b

• Within the context of the solution-diffusion model used to describe transport in nonporous films, L is given by

RTl

DSVL

• where D is the water diffusivity in the membrane, S is the water solubility in the membrane, V is the molar volume of water, R is the ideal gas constant, T is the ambient temperature, and l is the membrane thickness

• For an ideal solution, with complete dissociation of salt ions, osmotic pressure is defined as

CRT

• where π is the osmotic pressure, C is the salt ion concentration, R is the ideal gas constant, and T is the solution temperature.


RO transport Equations 2

• Salt passage through the membrane is not a function of pressure

• The salt flux is only a function of salt concentration

)( permeatefeeds CCBN

• where Ns is the salt flux through the membrane, B is the salt permeability constant describing the physical characteristics of the membrane, Cfeed is the salt concentration in the feed solution, and Cpermeate is the salt concentration in the permeate solution.


RO transport summary

• Thin Film Composite - give high flux, can operate at feed pressure up to 35 bar

• RO membranes are effectively non-porous. The transport of a molecule across the membrane is diffusion controlled

• Flow rate of water through the membrane is pressure dependent • The salt flux is only a function of salt concentration in feed

Handbook of Industrial Membrane Technology, M.C.Porter, 1990

SEM image of cross-section of a thin-film composite membrane


RO Equipment (1)• Water Quality Impacts

– Removal of dissolved solids (TDS reduction)– Removal of organics– Removal of silica (total SiO2 reduction)– Removal of other trace contaminants (i.e., boron, metals)

• Application Limitations– Is not an “absolute” treatment technology such as ion-

exchange (>99% for most ions, ~ 70-80% TOC)– Requires downstream treatment for contaminants (TDS,

TOC, SiO2, etc.) to achieve “ultrapure” water– Polymer membranes cannot tolerate oxidizers such as

chlorine, biocides, ozone– Reject stream (~ 25% of the feed) is near-saturation and

non-reclaimable– Chemical injection required: antiscalant, biocide, oxidant

reduction (bisulfite)– Periodic on-site membrane cleaning using aqueous

chemicals


RO Equipment (2)

Segmented Ring

Pressure Vessel

Pressure Vessel

Permeate

Concentrate

Permeate Plug

End Cap

End Cap/Membrane Element Adaptor

Brine Seals

Interconnector

O-Ring

Thrust Collar

End Cap/Membrane Element Adaptor

Feed

CONCENTRATE

( WASTE, BRINE, REJECT)

RO SYSTEM

FEEDWATER PERMEATE

PERMEATE PERMEATE

CONCENTRATE

TWO STAGE


RO membrane manufacture

• Hydranautics video of spiral wound membrane manufacture– http://www.membranes.com/

• Downloads– Download RO animation

• Dow Filmtec video of iLEC Interlocking Endcaps– http://www.dow.com/liquidseps/service/lm_install.htm

• iLEC Interlocking Endcaps Video


Ion Exchange (1)• Water Quality Impacts

– Removal of dissolved solids (TDS reduction) as ionic species

– Removal of ionized organics (TOC reduction)– Removal of silica (dissolved SiO2 reduction)– Removal of other trace contaminants (i.e.

boron/borate)

• Application Limitations– Is an “absolute” technology, completely removes

ionic species until resins “exhaust.” Requires frequent regenerations in high TDS applications (i.e. water softeners, primary beds)

– Because of leakage/exhaust issues, requires two IX mixed beds in series between the RO system and wafer Fab users for UPW, either one in primary and one in polish systems, or two in polish systems. Use of EDI can replace primary beds.

– Polymeric resins cannot tolerate oxidizers such as chlorine, biocides, ozone


Ion Exchange Beds (2)

Ca2+

Mg2+

K+

Na+

H+

Cl-

SO42-

NO3-

HCO3-

HSiO3-

OH-

Less affinity for ion

exchange sites so more difficult to

remove

Cation Exchanger Anion Exchanger

Affinity of ions

• Higher valence

• Higher MW

• Resin beads are made of Styrene and Di-vinyl-benzene with functional groups attached.

• Upon exhaustion all exchange sites are occupied by ions from solution and the bead is unable to remove additional ions.

• Regenerate with HCl and NaOH

• Analyse for Sodium, Silica and Boron – signal ion breakthrough and resin exhaustion.

Product Water>18 mOhms

(CH3)3N + OH

FOr Other Anion

Exchange

_

_

Na+OH-

SO3– H+

Na+

Or Other Cation

Exchange

H+Cl-

HB4O7-


Ion Exchange Beds (3)

• Mixed bed ion exchange resins i.e. they each bed has anion and cation resin (60:40 ratio – anion has less capacity).

• Separate resin based on different densities

Anion resin

Cation resin

Hydrochloric acid

Caustic

Regeneration chemicals to AW


Electrodeionistation (EDI)

Cl-, HCO3-, SO4

2-, Other Anions

Ca2+, Na+, H+, Other Cations

Feed Water

– – – – – –

+ +++++

Product Water>15 mOhms

Cation Concentrate

Anion Concentrate

Cathode

Anion Exchange Membrane

Anode

SALTSH+

OH-

Cation Exchange Membrane

• Water flows through the IX resin in the dilute chamber.

• Normal IX occurs to produce high purity water in the dilute chamber.

• Positive ions are drawn to the cathode through the cation selective membrane

• Negative ions are drawn to the anode through the anion selective membrane.

• The large electric potential between the electrodes cause water in the dilute chamber to split into H+ and OH- ions which regenerate the resin.


EDI (2)

Advantages

• Replaces regeneration chemicals

• Continuously regenerates resin system

• Robust mechanical systems.

• High performance and low maintenance

• Easily expandable.

Disadvantages

• Consumes high amount of power.

• Lots of piping involved in process, prone to leaks.

• Lots of parameters to monitor during operations.

• Difficult trouble shooting

EDI

Anion Mem.

OH-Ｈ＋

CL－

Ｈ＋OH-

Cathode Brine

Anode

Brine

Ion Exchanger ResinIon Exchanger Resin

Dilute

ＰDrainBrine Pump

DiluteCation Mem.

Anion Mem.

CL－

CL－

+

+ + ++

- - - - -Na+

Na+

Feed

EDI Chemical Free , Stand-by Bed Free

Regeneration

Waste Water

HCl

NaOH

Product

Feed

Ion Exchange Beds

Presented at UPW Expo, Philadelphia, PA Apr 2001


Typical Semiconductor Plant water use

BlendWater

Ultra Pure Water FAB

Cooling Towers

Air Scrubbers

Internal WaterTreatment

Internal Water Recycling

Internal Reclaim

CityWater

Application Water UseUltra-pure water 50 - 60%

Cooling towers 20 - 30%

Scrubbers 5 - 8%

Domestic, others 5 - 10%

Reclaim 20 – 30%

WWT Plant


Typical UPW system – block diagram

MAKE UP

1st Pass RO is main treatment step.

Pre-treatment steps required

PRIMARY LOOP

2nd Pass RO and IX are main

treatment steps.

POLISH LOOP

IX and UF are main treatment

steps

FAB

HUPW70 C

UPW PlantReclaim Drain

ULTRAPURE WATER November 2004


Typical UPW Plant Process Flow

http://www.liqui-cel.com/


Flow Diagram of Primary System

2B3T RO MB

Reclaim System

Pretreatment

Conventional System

EDI System

RO EDIReclaim System

PretreatmentMB

(Cation, Degas, Anion)



EDI System - pre-treatment

ProductConc.

HF Type UFPore Size -- 0.02um

Raw Water

Backwash

Filtration

Tank

ULP-RO(Operating Press. --100 psi)

EDI

Drain

Perfect Pretreatment Free RO CleaningUltra Low Pressure RO Low Power CostChemical Free No IX Regeneration

Perfect Pretreatment Free RO CleaningUltra Low Pressure RO Low Power CostChemical Free No IX Regeneration



UPW process efficiency improvement• High Efficiency RO (HEROTM)

FEED PERM.

REJECTMAXIMUM Reject pH is 11 for Membrane Warranty

HARDNESS AND ALKALINITY REMOVAL

(WAC and/or SAC)

DISSOLVED GAS REMOVAL

(FDG OR GTM)

TDS REDUCTION (HERO)

ALKALI

• Operating at high pH (~ 11) is the significant increase in rejecting weakly ionised anions such as organics, silica and boron.

• Strongly ionised species are also better rejected at high pH levels resulting in lower ionic loads on ion exchange beds.

• Pretreatment of the HEROTM feed water to remove hardness (Ca2+, Mg2+) and alkalinity (CO2) eliminates the potential for scale forming on the RO membrane allowing operation at high recoveries and flux.

Patent holder – Deb Mukhopadhyay


List of References• High-Purity Water Preparation for the Semiconductor, Pharmaceutical and Power Industries, Theodore H. Meltzer, Tall Oaks Publishing Inc. 1993

• Reverse Osmosis, A Practical Guide for Industrial Users, Wes Byrne, Tall Oaks Publishing Inc. 1995

• http://www.dow.com/liquidseps/

• http://www.membranes.com/

• http://www.liqui-cel.com/

dublin institute of technology msc in chemical and pharmaceutical process technology 30-apr-09...

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